The present invention relates to an electronic device equipped with a card interface, and more particularly to an electronic device suitable to set an operation mode for a card-shaped device connected thereto via the card interface.
Various types of electronic devices represented by personal computers generally have a function of using an IC card (PC card) based on the PCMCIA (Personal Computer Memory Card International Association). The PC card is used not only as a data storing medium but also for expanding its peripheral function. For example, there are some PC cards that function as a modem card, a network card, a hard disk drive, and a transmitter, etc.
Further, in recent years, IC cards smaller than the PC cards are being used as well as the PC cards. One of these small IC cards is a small memory card that has a flash memory for storing various types of digital  data represented by image data or music data. As is well known, the flash memory is a non-volatile memory, which is electrically programmable and has its stored contents kept as they are even when power supply is interrupted. In such small memory cards having a flash memory, in general, only one of a plurality of pins is used as a data pin (data line). Accordingly, the small memory cards execute 1-bit data transfer.
Furthermore, a small memory card called an “SD (Secure Digital) memory card” is also available. The SD memory card has been developed by Matsushita Electric Industrial Co., Ltd., SanDisk Corporation and Toshiba Corporation. The SD memory card has nine signal pins, four of which can be used as data lines. Thus, the SD memory card realizes 4-bit data transfer, which means that it has a higher data transfer capacity than the previous small memory card that executes 1-bit data transfer.
As another small card, there is an I/O card having an I/O (Input/Output) interface function. After the appearance of the SD memory card, it is requested that such a small I/O card and the SD memory card can be used through a common card slot formed in an electronic device (a host) such as a personal computer, as in the case of the PC cards. To enable a small memory card, such as the SD memory card, and various types of small I/O cards to be commonly used in an electronic device,  it is necessary to give those cards, for example, the same pin arrangement and the same shape. Even in this case, however, the following problem will occur.
In small memory cards, many of the pins provided therein are used as data lines to enhance their data transfer capacity. For example, in the SD memory card, four of the nine pins are used as data lines as aforementioned. Accordingly, if the same pin arrangement and the same shape are imparted to the small memory cards and the small I/O cards, many pins are used for data transfer between an electronic device and each small I/O card. Using a lot of pins as data lines to enhance the data transfer capacity is effective in the case of a card-shaped device such as a memory card, which does not execute data transfer so often but transfers a large amount of data at one time. On the other hand, it is not so important to enhance the data transfer capacity in the case of a card-shaped device such as an I/O card, which executes data transfer (i.e. transaction) many times although it does not transfer a large amount of data at one time. It is more important to start data transfer quickly, i.e. to increase the speed of a response.